MERS, the worrisome new virus that has killed 38 people in the Middle East, appears to be a serious risk to hospitals where it transmits easily, infectious disease experts said in a report Wednesday.

But they added the virus might not present the same risks to those outside hospital – a feature of MERS’ better-known and related coronavirus, SARS, which devastated the Toronto hospital system when it emerged in 2003.

The researchers assembled their findings into a report published Wednesday in the New England Journal of Medicine. In their report, they explain what they learned about Middle East Respiratory Syndrome based on an outbreak from April 1 to May 23 that infected 23 people in four hospitals in the Eastern Province of Saudi Arabia.

It’s the first large-scale look of what is happening with MERS in the Arabian kingdom, which has shared little information with the outside world about its outbreak.

The report’s authors, all experts in SARS, including Dr. Allison McGeer, an infection control expert at Toronto's Mount Sinai Hospital, travelled to Saudi Arabia in May to investigate the outbreak and to compare it to SARS.

They write in their report that MERS appears to be deadlier than SARS, having killed 11 of the 23 people it infected in the one outbreak.

The virus also appears to spread easily among hospital patients, as well as between hospitals. In the outbreak they studied, MERS caused infections in several family members of infected patients as well as in two health-care workers.

The researchers note though that one aspect distinguishes MERS from SARS: It has infected relatively few healthy health-care workers.

Infectious disease expert Dr. Neil Rau, who was not involved in the study but remembers the SARS outbreak in Toronto well, says the lack of spread is a key point.

“It’s in contrast to SARS, where an otherwise healthy nurse could take ill … and be infecting family members who then become extremely ill. (With MERS), it’s mainly patient-to-patient where you have serious disease occurring,” he told CTV’s Canada AM Thursday.

But Rau noted that MERS appeared to spread easily between the four hospitals. Eight of the infected patients studied had been transferred between facilities or hospitals, which led to more patients becoming exposed.

Rau says the ease this virus has in spreading among hospitals is worrisome.

“If we had something like this circulating here, we could be re-living some of the horrors of SARS -- though what I would call ‘SARS lite,’ because you don’t have the health-care worker component being as serious,” he said.

Rau says it appears MERS is fairly similar to SARS in its infectiousness or contagiousness. And unfortunately, like SARS, the disease is hard to identify at first. MERS’s initial symptoms of bad cough and fever make it look like any other viral respiratory illness -- until the symptoms begin to worsen badly.

The good news, Rau notes, is that the U.S. CDC has already developed diagnostic tests to spot MERS – tests which weren’t available early on in the SARS outbreak. That’s allowed hospitals around the world, including Canada, to now screen patients for MERS.

“So somebody who has been to the Arabian peninsula in the last 14 days who has a fever and cough would be treated differently in hospital, right from the emergency-room level,” he says.

Another aspect that distinguishes MERS from SARS, the report notes, is that MERS patients appear to be infectious earlier in their illness than SARS patients were. When patients are most contagious late in illness, it’s easier to diagnose and isolate them before they infect others. So an illness that’s most contagious early on is more worrisome.

They also note that it appears that MERS, although it has infected only 60 or so people so far, has a death rate of 48 per cent – much higher than the 8-per-cent mortality rate of SARS, which infected more than 8,400 people in 31 countries before petering out.

MERS was first identified in Saudi Arabia and Jordan, though cases have since been reported in Qatar, the United Arab Emirates and Tunisia. As well, cases have been imported into France, Britain and Italy.

The World Health Organization says the worldwide toll now stands at 38 deaths from 64 laboratory-confirmed cases. The origin of the virus is still unclear.

Since the beginning of April, Saudi Arabia has recorded 40 of those cases but has revealed little information about how widespread the problem there is.

With files from The Canadian Press